1. Field of the Invention
The present invention relates to an optical compensation film, a polarizing plate and a liquid crystal display apparatus.
2. Background Art
The market of thin-type displays has been upsurging in recent years. Specifically, the enlargement of the market of liquid crystal display apparatuses is profound. Liquid crystal display apparatuses are under way of development for use not only in personal computer monitors but also for TV. Display size is therefore increasingly larger, so high definition has been investigated more actively. Accordingly, still more demands exist toward the improvement of the performances of individual members contained in liquid crystal display apparatuses.
In particular, IPS-mode liquid crystal display apparatus is promising as a liquid crystal display apparatus for large TV. As demands for high definition of IPS (In-Plane-Switching) mode, improvements of those described below are now desired: (1) contrast reduction due to the occurrence of “light leakage” when observed during black display along an oblique direction and (2) color change of images when observed during black display along an oblique direction.
As approaches to improve the viewing angle dependency of contrast and color in these two problems, it is proposed to arrange an optical compensation film with an optical anisotropic layer containing a polymer with negative inherent birefringence and a vertically oriented discotic liquid crystal. (See JP-A-10-54982 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-9-292522) However, the optical performance demanded for an optical compensation film of IPS mode requires the increase of the refractive index along the film thickness direction, to adjust the retardation Rth along the film thickness direction to negativity. However, such performance has not yet been achieved in these films. Additionally, it is difficult to control the orientation along the film thickness direction. Thus, an appropriate optical compensation film with a negative Rth value has been desired.